Forestry and agriculture are frequently concerned with planting or replanting extensive acreage for crop production, reforestation, land reclamation, and other similar purposes. Although some crops or stands or timber restock naturally, planting or replanting generally requires manual assistance either by seeding the field production site or by planting nursery-grown seedlings thereon. Particularly with regard to reforestation and afforestation, the preferred method of planting is by the transplantation of seedlings rather than by direct seeding. In this manner, control over the development of the seedlings can be closely maintained by supervision of soil conditions, fertilization, irrigation, growth characteristics, and related factors. High quality planting stock can thereby be produced for transplantation, and the problems attendant to seed germination and initial growth of the seedling can be avoided in the field.
Automated systems are currently used to plant seedlings for the production of a harvestable crop or stand of trees. In order to take advantage of such systems, however, it is necessary to produce individual and discreet seedlings that can be singularly fed to automatic devices. Thereby, the crop or stand can be planted with the desired density or concentration by positioning the seedlings singularly within the ground surface and by regulating the spacing between the seedlings. Kolk et al. U.S. Pat. No. 3,872,805 illustrates such an automated device which plants rooted seedlings at regular intervals as the machine advances.
The process of providing individual seedlings for transplantation is known as seedling singularization, and such can be achieved upon planting of the seeds in a seedbed, while the seedlings are growing in the bed, at the time the seedlings are lifted, or when the seedlings are sorted prior to transplantation. To reduce manual operations, including removal of extraneous and intertwined seedlings, singularization at the time the seeds are planted in the seedbed is preferred. Such is commonly achieved by precision seeding, i.e., planting the seeds in a uniformly spaced array wherein a single seed occupies the center of a plot of predetermined dimensions.
Precision seeding furthermore produces additional benefits in that uniform seedlings are produced, which are more amenable to automatic planting. For example, seed spacing studies have shown that the optimum spacing for loblolly pine seeds is one seed per 2- by 3-inch plot, or 16 rows in a 4-foot seedbed, so as to provide a seeding density of 24 seeds per square foot. Under such conditions large and uniform seedlings are produced, and the extent and degree of sorting and grading are commensurately reduced. By precision seeding, maximum utility is made of the nursery growing area and postseeding operations are facilitated.
Automatic precision seeding is typically performed by devices which meter a supply of seeds onto a seedbed by selecting individual seeds from the supply at a predetermined rate or density, transporting the seeds to the vicinity in which the seeds are to be planted, and discharging the seeds onto the seedbed. The efficiency and accuracy with which these functions are performed, however, varies according to the structural limitations of the particular devices. For example, Whipple U.S. Pat. No. 3,387,746 discloses a rotary-type planting device that singly delivers seeds to a seedbed by means of a rotating metering wheel which carries the seed from a seed chamber to discharge channels or tubes positioned above the seedbed. A vacuum is applied to ports on the wheel as they rotate through the seed chamber and to the discharge channels thereby selecting and delivering singular seeds. When the ports are positioned above the discharge channel, compressed air drives the seed from the port and through the delivery channels to the seedbed.
Seed placement by the planting device disclosed in the Whipple patent would appear to be imprecise. Because the seed is dropped or blown in a vertical distance down the discharge channels and to the seedbed, there would be a tendency for the seed to scatter upon impact with the soil, thereby producing uneven and staggered spacing. Furthermore, the passage of the seeds into and out of the ports and through the discharge channels is more likely to cause damage to the seeds thereby eliminating the advantages derived from handling the seeds with a vacuum system. The greater disadvantage, however, is the absence of any means by which the seed can become implanted into the soil of the seedbed. With no method or apparatus for covering the deposited seed or for pressing the seed into the soil, the seed is subject to being removed by predators or displaced by winds or water drainage.
A planting apparatus having the capacity to close a previously opened furrow into which seeds have been deposited is illustrated in Tweedale U.S. Pat. No. 3,156,201. By this device, a ground engaging press wheel, separate from the seed metering drum, travels at the trailing end of the planter and pushes soil over the deposited seed. When precision seeding with seeds spaced as close as 2 inches is desired, however, this method of covering the seed would seem to cause further disruption of the uniform array of seeds since pushing the soil would move the seeds from their deposited location.
The metering drum in the Tweedale patent has other limitations in that the seeds must drop a vertical distance to the seedbed. As explained above, scattering can result from this practice. In addition, the metering drum is subject to spacing the seeds on the seedbed at variable distances with changing speeds of rotation of the drum relative to the rate at which the apparatus is advanced. When the relative speed is other than zero, however, scattering of the seed can result because of the horizontal velocity imparted to the seed, consequently affecting the uniform spacing between seeds.
It is accordingly an object of the present invention to provide a seed planting apparatus that is adapted to continuously meter seeds onto a seedbed or the like and simultaneously press the seeds into the soil.
A further object of this invention is to provide an automatic precision seeding appratus which is capable of containing seeds preparatory to planting, metering the seeds according to predetermined spacing and density, transporting the seeds to the seedbed, releasing the seeds on the seedbed, and implanting the seeds within the soil.
It is another object of the present invention to provide a seed planting apparatus that distributes seed on the seedbed in a predetermined, uniformly spaced array so that seedling singularization is facilitated. In this connection, it is also an object of this invention to provide an apparatus that seeds multiple rows in the direction of travel and with close proximity between rows and successive seeds to produce a high density of seeds per unit of seedbed surface area. Also in this regard, another object of the present invention is to provide a seed planting aparatus which is capable of seeding at a density that is independent of the ground speed at which the apparatus moves.
Another object of this invention is the provision of a seed planting apparatus that transports the seeds to the seedbed by means of a vacuum system, whereby the seeds are handled with a minimum of damage and so that predominantly singular seeds are planted to a predetermined plot of given dimensions on the surface of the seedbed.
Still another object of the invention is the provision of a seed planting apparatus that is adapted to operate on nursery prepared seedbeds or in the field for either direct seeding or the preparation of seedlings for subsequent transplantation.